LEARN KOREAN (한국어) [GRAMMAR] #1

잘: WELL

Just like 잘하다, you can use the word 잘 in sentences to indicate that one does something well. Usually, when you remove 하다 from a word, the word without 하다 becomes a noun. In this case, removing 하다 from 잘 does not make 잘 a noun. Instead, it is an adverb. The only reason this is important is so that you know that you can use 잘 in sentences just like other adverbs, in this case to mean "(to do something) well." It is essentially the same as "잘하다," but used slightly different. For example:

그 주인은 고객님들을 잘 대우해요 - That owner treats the customers well
나는 어젯밤에 잘 잤어 - I slept well last night

When I first learned about 잘하다 and 잘, I was trying to understand if these two sentences were the same:

나는 공부를 잘해 - I study well
나는 잘 공부해 - I study well

The answer: essentially, but not entirely.

The difference is so subtle that you don't really need to worry about it. However, when I learned this, I worried about it, so I think maybe you should worry about it too. The reason I say "don't worry about it" is because now when I speak I can't really distinguish the difference in meaning. The only way I could tell the difference is referring back to my old notes. Nonetheless, there is a subtle difference:

나는 공부를 잘한다 - I study well, or
"나는 (noun)을 잘한다" means that, in general, your ability to do something is good. However,

나는 잘 공부한다 - I study well, or
"나는 잘 (verb)다" means that you can study well because of some situation (for example, maybe you have a test coming up and you are studying really hard because of that situation).

But really, don't get too caught up on the difference between the two. Especially since sometimes they look and sound almost exactly the same. If you separated 공부 and 하다 in the second example, you would get:

나는 공부를 잘 해 - I study well, which sounds (and almost looks) exactly the same as:
나는 공부를 잘해 - I study well

Anyways, don't worry about it too much.

You already know the word 잘생기다 means "handsome." That word is actually 잘 and 생기다 put together. 생기다 has a lot of meanings, but putting 잘 and 생기다 together, it sort of means "to come out well." The opposite is true for 못생기다 (to be ugly).

Always remember to not translate directly from English to Korean, as there are so many things that are not 100% the same in both languages. For example, in English, we would never say "I don't know well," but in Korean, it is very common to say:

저는 잘 모르겠어요* - I don't know (well)
*Also notice that the future tense 모르다 is used here. Even though it is in the present, 모르겠다 is used very commonly to indicate that you don't know something – Even though it directly translates to "I will not know."